1. Field of the Invention
The invention relates to a mechanically shiftable three speed planetary gearing unit or transmission. 2. Description of the Prior Art
A two stage planetary gearing with step-down gearing is known from German Patent Publication Published for Opposition Purposes No. 22 51 299 where a coupling sleeve, which is toothed on the inside and outside, is used in a sliding manner. The step-down gearing components of this gearing known from the above-mentioned patent remain engaged or meshed in the shift stage with direct penetration. The step-down gearing components continue to run on idle in this shift step. The result of this is an increase in the wear and tear factor of the toothing and the bearings of the planetary gearings. Additionally, the revolutions per minute of the driving shaft are limited by kinematic conditions of the step-down gearing.